1. Field of the Invention
The present invention relates to a lens barrel assembly having an iris diaphragm device, and a projector. More particularly, the present invention relates to a lens barrel assembly having an iris diaphragm device, and a projector, in which rotation of a part can be reliably transmitted to a part included in the iris diaphragm device.
2. Description Related to the Prior Art
A lens barrel assembly for use with a projector is known, and operated for enlarging image light to project an image to a screen. The lens barrel assembly includes a stationary barrel, a rotatable barrel and an iris diaphragm device. There are linear grooves formed in the stationary barrel. There are cam grooves formed in the rotatable barrel. Lenses/lens groups in the rotatable barrel are moved in a direction along an optical axis according to the linear groove of the stationary barrel for zooming. The iris diaphragm device is disposed at a rear end of the stationary barrel or between lenses/lens groups, and adjusts brightness of an image projected to the screen.
JP-A 6-265972 discloses the iris diaphragm device, which includes a support ring, a driving ring and plural diaphragm blades disposed between the support ring and the driving ring. The diaphragm blades are pivotally movable on the support ring. A cam slot guides the diaphragm blades on the driving ring. When the driving ring is rotated, the diaphragm blades are moved pivotally, so that an aperture opening can be enlarged or reduced.
Various types of structures for changing the aperture opening of the iris diaphragm device are known. See JP-A 2001-290190. A first one of those is a manual type in which an operable aperture ring is disposed around the lens barrel assembly. A diaphragm control plate portion or lever is caused by rotation of the aperture ring operated manually or mechanically to rotate the driving ring. A second one of the types is a motor drive type in which a small motor is incorporated in the lens barrel assembly. The motor is driven to rotate the driving ring.
In the manual type, it is necessary between the aperture ring and the driving ring to dispose the diaphragm control plate portion in a manner offset from the rotatable barrel. Thus, the diaphragm control plate portion has a long shape in a direction along the optical axis. A guide device is used for guiding the diaphragm control plate portion in a manner rotatable about the optical axis of the stationary barrel without play. However, there occurs a problem in that a cumulative error of the diaphragm control plate portion with the guide device may be created according to errors of parts and/or errors of assembly. It is likely that the diaphragm control plate portion becomes offset rotationally about the driving ring by rotation of the aperture ring because of the long shape in the direction along the optical axis. Failure of transmitting rotation of the aperture ring to the driving ring will occur seriously.
Also, a problem arises in the motor drive type in that reduction of a size of the lens barrel assembly is far more difficult than that of the manual type. A manufacturing cost of the motor drive type is considerably high.